Unidirectional rotation actuator

ABSTRACT

A unidirectional rotation actuator comprising a cylinder, a piston for undergoing sliding reciprocation within the cylinder, a cam groove formed in either the cylinder or piston in the surface thereof confronting the other, and a cam follower secured to the other confronting surface and engaged with the cam groove, the cam groove having a shape such that the piston, as it is driven by a working fluid in reciprocating motion, is simultaneously rotated intermittently in only one direction relative to the cylinder. For this purpose, the cam groove comprises a plurality of straight groove parts of alternately different inclinations in zigzag configuration and guide groove parts positioned at and forming junctures of adjacent straight groove parts, each guide groove part functioning to guide the cam follower which has relatively passed along one straight groove part into the succeeding straight groove part.

United. States Patent [1 1 Ishii et al.

[111 7 3,869,928 1Mar.1l,1975

1 1 UNIDIRECTIONAL ROTATION ACTUATOR [75] Inventors: Akemi Ishii, Kawasaki; Syotaro Suda, Yokohoma, both of Japan [73] Assignee: Tokico Ltd., Kawasaki-ku, Kawasaki City, Japan [22] Filed: Sept. 4, 1973 [21] Appl. No.: 393,833

[30] Foreign Application Priority Data Sept. 5, 1972 Japan 47-89005 Sept. 26, 1972 Japan 47-96842 Sept. 27, 1972 Japan 47-96791 52 us. Cl. 74/88 [51] Int. Cl. Fl6h 27/02 [58] Field of Search 74/88 [56] References Cited UNITED STATES PATENTS 3,071,015 l/1963 Donguy 74/88 3,703.104 11/1972 Tamplen 74/88 FOREIGN PATENTS OR APPLICATIONS 932,273 7/1963 Great Britain 74/88 Primary Examiner-Benjamin W. Wyche Assistant ExaminerWesley S. Ratliff, Jr.

[57] ABSTRACT der, a piston for undergoing sliding reciprocation within the cylinder, a cam groove formed in either the cylinder or piston in the surface thereof confronting the other, and a cam follower secured to the other confronting surface and engaged with the cam groove, the cam groove having a shape such that the piston, as it is driven by a working fluid in reciprocating motion, is simultaneously rotated intermittently in only one direction relative to the cylinder. For this purpose, the cam groove comprises a plurality of straight groove parts of alternately different inclinations in zigzag configuration and guide groove parts positioned at and forming junctures of adjacent straight groove parts, each guide groove part functioning to guide the cam follower which has relatively passed along one straight groove part into the succeeding straight groove part.

3 Claims, 16 Drawing Figures mmn News 2. 869.928

SHEETS 0F 8 pmm gmu 1151.3

SHEET 5 OF 8 FIG. 4A FIG. 4B 53 51. 55 56 53 54 55 56 1 1 11 50 I 1 1 1 .L i .L .L J .L .L .L

T T T 521 151 52,1 51

FIG. 40 FIG. 4E 53 54 55 5s 53 54 55 56 FIG. 4F

iJ/L

PATENTEUHARI 1 1975 "-%.869.928

' sum 7 of 8 1 UNIDIRECTIONAL ROTATION ACTUATOR BACKGROUND or THE INVENTION The present invention relates generally to a unidirec tional rotation actuator and more particularly to an actuator having a piston driven by a working fluid to undergo reciprocating motion and, as caused by a cam mechanism, to rotate in a single direction interrelatedly with its reciprocating motion, this rotation being utilized as the output of the actuator.

Among unidirectional rotation actuators known heretofore in which working fluids are utilized as motive power source, there is a device in which the reciprocating motion of a piston driven by a working fluid is converted by a crank mechanism into a unidirectional rotation.

This known actuator undergoes a movement corresponding to a sine curve, however, whereby variations in the rotational torque of the output shaft disadvantageously occur. Another problem accompanying this known device is that, since a braking device has been used for stopping the rotation output shaft at a specific position for each intermittent rotation, it has been difficult to stop the output shaft at the specific position.

SUMMARY OF THE INVENTION Accordingly, it is a general object of the present invention to provide a new and useful unidirectional rotation actuator in which the above described difficulties have been overcome.

A specific object of the invention is to provide a unidirectional rotation actuator which produces a rotational output intermittently in only'one direction. In accordance with the invention, the rotation stopping position after each intermittent rotation ofa rotating structure is determined with high precision.

Another object of the invention is to provide a indirectional rotation actuator in which, by use ofa mechanism comprising a cam groove of zigzag shape made up of a plurality of straight groove parts continuously joined end-to-end with alternately different inclinations and a cam follower engaged with this cam groove, an intermittent rotational output is produced each time the cam follower moves along one of the straight groove parts. As the cam follower reaches each bend in the zigzag cam groove, that is, the junction of two adjacent straight groove parts, the intermittent rotation is temporarily stopped. For this reason, a braking device is not necessary for stopping the intermittent rotation. Furthermore, since the elemental parts of the cam groove are straight, the rotational torque is always con stant.

Still another object of the invention is to provide a unidirectional rotation actuator which is suitable for application in a selector valve, control valve, or changeover valve for carrying out valve changeover or switching with each intermittent rotation.

Further objects and features of the invention will be apparent from the following detailed description with respect to preferred embodiments of the invention when read in conjunction with the accompanying drawings, throughout which like parts are designated by like reference numerals and characters.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a longitudinal section of a first embodiment of a unidirectional rotation actuator according to the present invention;

FIG. 2 is a developed plan view indicating the shape of a cam groove formed around the outer cylindrical surface of the piston of the actuator shown in FIG. 1;

FIG. 3 is a longitudinal section of a second embodiment ofa unidirectional rotation actuator according to the invention;

FIGS. 4A through 4F are diagrams respectively indicating the valve changing over operation of a changeover or selector valve to which the actuator of the invention is applied;

FIG. Sis a longitudinal section of one embodiment of specific structure of the changeover valve indicated in FIGS. 4A through 4F;

FIG. 6 is a cross section taken along the line VI-VI in FIG. 5;

FIG. 7 is a longitudinal section taken along the line VII-VII in FIG. 6;

FIG. 8 is a longitudinal section taken along the line VIIIVIII in FIG. 6;

'FIGS. 9A and 9B are diagrammatic perspective views for a description of the operation of the changeover valve device illustrated in FIGS. 5 through 8; and

FIG. 10 is a schematic diagram showing the general organization of a system for sprinkling or spreading ag ricultural chemicals in which changeover valve mechanisms utilizing the actuator of the invention are employed.

DETAILED DESCRIPTION With reference to FIGS. 1, 2, and 3, first and second embodiments of the unidirectional rotation actuator according to the invention will first be described.

FIGS. 1 and 2 illustrate on embodiment of the actuator of the invention.

A piston 10 is slidably and rotatably fitted in a fixed cylinder 11, the displacement of the piston 10 in its axial direction being limited at positions where the two end surfaces of the piston abut against the corresponding head or end wall surfaces of the cylinder 11. The end walls ofthe cylinder are respectively provided with ports 12 and 13, which communicate with recesses 11a and 111) formed in the inner sides of the end walls. Pipe lines 14 and 15 arerespectively connected at their ends on one side to the ports 12 and 13 and at their other ends to an electromagnetic four-way valve 16.

The piston 10 is provided around its outer cylindrical surface with a continuous cam groove 17 of zigzag shape as shown in a developed view in FIG. 2. A cylindrical cam follower 18 projects into the interior of the cylinder 11 to enter and engage with the cam groove 17 and is thus fixedly held by means such as a holder 19 disposed within the cylindrical sidewall of the cylinder 11 at substantially the midpoint position in the axial direction of the cylinder.

This cam follower 18 is secured by a nut 30 to the holder 19, which is held fixedly in place by a cover 31 secured to the cylinder; 11 by bolts 32.

An output shaft 21) extends through and is rotatably held by one end wall of the cylinder 11 and extends at its inner end to a position which is substantially at the midpoint of the cylinder 11 in the axial direction thereof. This output shaft 20 is prevented from being displaced in its axial direction by rings 21 and 22 engaged with the inner and outer parts of the cylinder end wall through which the shaft extends. Furthermore,the inner end of the output shaft 20 extending into the cylinder 11 is slidably engaged with a central through bore 10a formed through the piston 10, and a slide key 23 fixed to the output shaft near its inner end is slidably engaged in a key groove 10b formed in the wall of the bore 10a in the longitudinal direction thereof. Accordingly, the piston 10 can slide axially within the cylinder 11 independently of the output shaft 20 but is caused to rotate unitarily with the shaft 20 about its axis.

A screw plug 24 is screwed into the piston 10 at its end near the inner end of the output shaft 20 thereby to close the end of the bore 10a and thereby to completely isolate from each other the cylinder chambers A and B onopposite sides of the piston 10 within the cylinder 11. In addition, packings such as O-rings 25 are provided at appropriate parts to ensure tightness against leakage of the working fluid supplied into the cylinder 11.

The shape of the aforementioned cam groove 17 formed in the outer cylindrical surface of the piston 10 will now be described in conjunction with FIG. 2, which is a development into a plan view of the cylindrical outer surface of the piston 10. The cam groove 17 is made up of straight grooves 17a through 17fconsecutively joined in zigzag formation at bends spaced apart by 11'D/6 around the outer circumference 1TB of the piston l0.

The above mentioned groove parts 17a through 17f are respectively of straight form, and the cam groove 17 is of zigzag configuration made up of groove parts 17a, 17c, and l7e inclined in one direction and groove parts 17b, 17d, and 17f inclined in an opposite direction, these groove parts of different inclination being alternately disposed in continuously joined arrangement. At the bends in this zigzag groove formation, there are formed guide groove parts 26a'through 26f into which the cam follower 18 is introduced for the purpose of causing the piston .10 to rotate in the same direction. The part of the outer cylindrical surface of the piston 10 in which the groove parts are formed is of somewhat smaller diameter then the parts thereof near the upper and lower ends thereof in contact with the inner wall surface of the cylinder 11.

The configuration of the cam groove parts 17a through 17]" and the guide groove parts 26 will now be considered in detailed with reference to FIG. 2. Points 02, 04, and 06, on line E and points 01, 03, and on line F indicate the relative center positions of the cam follower 18 when the piston is at its highest position and at its lowest position (as viewed in FIG. 1), respectively. Lines G and H are imaginary lines positioned at a specific distance above and below the lines E and F, respectively.

Lines Tl through T6 are respectively the centerlines of the zigzag grooves 17a through 17f, which have widths slightly greater than the diameter of the cam follower 18. The intersections with the line E or F of the extensions of the centerlines T1 through T6 in the direction opposite to the direction (arrow C direction in FIG. 2) for causing the piston 10 to rotate are here designated by reference characters 01 through 06. Furthermore, the intersections with the centerlines T2, T3, T1, T6 of vertical lines drawn toward the centerlines T2, T3, T6, T1 from the intersections 01 through 06 are here designated by reference characters s1, s2, s5, s6.

The guide groove part 26a between the groove parts 17a and 17b has a contour determined by the envelope line of the movement of the cam follower 18 as it is caused to move along the centerline T1 to the point 01 and further caused to descend vertically to the point s1. The groove parts 17a and 17b are contiguously joined to and communicate with this guide groove part 260. The contours of the guide groove parts 26b, 26c, 26fare similarly determined. The points 01 and 06 are atpositions dividing the outer circumference of the piston 10 into six equal divisions. these positions being offset respectively to the left of the points at which the nearest pair of groove parts intersect.

Next, the operation of the actuator of the above described construction will be described. In FIG. 1, the solenoid 27 is deenergized, and a port 16a of the fourway valve 16 is connected to the pipe lines 14 and 15. Accordingly, the working fluid such as compressed air or oil is supplied through the pipe line 14, a throttle valve 29, and port 12 to the chamber A of the cylinder 11, and the piston 10 descends under the guidance of the cylinder 11 and the output shaft 20. When the piston 10 is at its lowest position, the cam follower 18 is positioned within the-guide groove part 26a.

When the solenoid 27 is energized, the four-way valve 16 operates to connect its port 161; to the pipe lines 14 and 15. Accordingly, the working fluid is conducted through the pipe line 15 and, passing by a throttle valve 28, is supplied through the port 13 into the cylinder chamber B. Consequently, the piston 10 starts to ascend. On one hand, as the piston 10 rises, the working fluid filling the chamber A is discharged through the port 12 and the pipe line 14. The velocity of movement of the piston 10 can be suitably set by adjusting the variable throttling valves 28 and 29.

Assuming that the cam follower 18 starts its operation from the point 01, the vertical surface of the guide groove part 26a being guided the cam follower 18. Since thepoint 01 is offset to the left (as viewed in FIG. 2) from the intersection of the centerlines T1 and T2, the cam follower 18 always contacts and presses against the inclined wall surface of the groove part 17b as a result of the rise of the piston 10. Consequently, as the piston 10 continues to rise, it rotates in the arrow C direction, its inclined groove part 17b being guided by the cam follower 18.

As the piston 10 reaches its highest position determined by the cylinder 11, the cam follower 18 slides along the groove part 17b and enters the guide groove part 26b, at which position the piston 10 has rotated 60 from its position indicated in FIG. 1. This rotation of the piston 10 is transmitted by way of the slide key 23 to the output shaft 20, whereby the output shaft 20 rotates 60 degrees together with the piston 10.

When, with machine in this operational state, the solenoid 27 is again deenergized, the direction of flow of the working fluid within the pipe lines 14 and 15 is reversed, and working fluid is supplied to the chamber A to impart a force urging the piston 10 to move downward. The piston descends vertically, the vertical surface of the guide groove part 26b being guided by the cam follower 18, which then comes into pressing contact with the inclined wall surface of the groove part adjacent to the groove part 17b.

Accordingly, as the piston 10 continues to descend, it rotates in the same direction as in the above described case, its inclined groove part 17c being guided by the cam follower 18. When the piston reaches its lowest position determined by the cylinder 11, the cam follower l8, guided along the groove part 170, enters into the guide groove part 260, whereupon the piston 10 has been rotated a further 60 degrees from its rotational position corresponding to its highest position.

As is apparent from the above description, by repeatedly rendering the solenoid 27 into energized and deenergized states, the flow direction of the working fluid through the pipe lines 14 and I5 is alternately reversed, and the piston undergoes a repetition of a rising stroke and a descending stroke and, at the same time,is rotated through a constant 60 of angle in the same direction for each stroke. The rotation of the piston 10 is transmitted to the output shaft 20, which thereby is rotated intermittently in the same direction through a constant angle each time, that is, as highly precise indexing is carried out.

In the above described embodiment of the invention, the guide groove parts 26a through 26fare provided at positions dividing the circumference of the piston 10 into six equal intervals, and the output shaft is caused to rotate in the same direction by increments of 60 degrees of angle as the piston 10 undergoes repeated ascending and descending strokes. The number of these guide groove parts is not necessarily limited to six, however. That is, by using n guide groove parts disposed at equally spaced intervals, it is possible to make the rotational angle of the output shaft 20 resulting form one stroke of the piston 10 equal to 360/n.

Furthermore, by disposing the guide groove parts at positions, not with equal spacing, but with unequal spacing, the output shaft 20 can be caused to undergo intermittent rotation strokes varying angles as a result of the stokes of the piston 10. It will be observed that since the cam groove 17 is formed continuously around the outer peripheral surface of the piston 10, the number of the guide groove parts, that is, the number of bends in the cam groove, is always an even number.

In the case where, in forming the guide groove parts at the bends in the cam groove 17, the direction of extension of the inclined groove part is made opposite to that in the above described embodiment, the output shaft 20 is rotated through constant angle intervals only in directions opposite to that mentioned above as the piston 10 undergoes ascending and descending strokes. Furthermore, since each stroke of the piston 10 is restricted between the lines E and F in FIG. 2 by the longitudinal dimension of the cylinder 11, the forming of each guide groove part 26 with a further elongation of the extension part of the inclined groove part will have no deleterious effect whatsoever on the operation of the actuator.

A second embodiment of the unidirectional rotation actuator according to the invention will now be described in conjunction with FIG. 3, in which parts which are the same as those in FIG. 1 are designated by like reference numerals and characters. Detailed description of these parts will not be repeated.

In this second embodiment, a cam groove 42 of the same or similar contour as the cam groove 17 in the first embodiment is formed in the inner wall surface of the lower half part of a cylinder 41. A cam follower 43 engaged with this cam groove 42 is embeddedly fixed at its root end to the outer cylindrical surface of a piston 40 near the lower end thereof, this piston 40 being slidably provided within the cylinder 41.

A guide groove part 44 at the lower side of the cam groove 42 is extended to the lower end of the cylinder 41 in order to facilitate the forming of the cam groove 42 and to facilitate'the engagement of the cam follower 43 with the cam groove 42 at the time the piston 40 is fitted into the cylinder 41. g

The operation of the actuator in this second embodiment thereof is similar to that in the preceding first embodiment. That is, a solenoid is repeatedly energized and deenergized to changeover the four-way valve 16 thereby the repeatedly reverse the direction of flow of a working fluid'through pipe lines 14 and 15. As a result, the piston 40 undergoes repeated ascending and descending strokes relative to an output shaft 20 and the cylinder 41, whereby the output shaft 20 is rotated intermittently in onedirection through a constant angle for each piston stroke.

While, in the above described first and second embodiments, the cylinder 11 (or 41) is stationary, and the piston 10 (or 40) is driven in up-and-down movement to drive the output shaft 20 in intermittent rotation, it is also possible to provide an actuator in which the shaft 20 is stationary, and the cylinder 11 (or 41) is caused by the reciprocating motion of the piston 10 (or 40) to undergo intermittent rotation through specific angular increments.

One embodiment of a changeover valve device in which the actuator of the invention is applied will now be described, the fundamental operation of this device being first considered in conjunction with FIGS. 4A through 4F. This changeover valve device 50 is provided with two flow inlets 51 and 52 and four flow outlets 53, 54, 55 and 56.

Initially, this device 50 is in the state indicated in FIG. 4A, that is, the state wherein the flow inlets 51 and 52 are shut off from the flow outlets 53, 54,55 and 56. Next the device 50 assumes the state indicated in FIG. 48 wherein the flow inlet 51 is communicated with the flow outlet 53, and the first fluid entering through the inlet 51 is discharged through the outlet 53. Then the device 50 assumes the state indicated in FIG. 4C wherein it is changed over so that the inlet 51 is communicated with the outlet 54, and, at the same time, the inlet 52 communicates anew with the outlet 53. Through the outlet 54, the first fluid entering through the inlet 51 is discharged, while through the outlet 53, a second fluid entering through the inlet 52 is discharged.

Similarly, when the changeover valve device is in the state indicated in FIG. 4D, the inlet 51 is communicated with the outlet 55, and the inlet 52 is communicated with the outlet 54. In the state indicated in FIG. 4E. the inlet 51 is communicated with the outlet 56,

while the inlet 52 is communicated with the outlet 55. 7

Further, in the state indicated in FIG. 4F, only the inlet 52 is communicated with the outlet 56.

In this manner, the changeover valve device 50 is successively changed over in the sequence indicated in FIGS. 4A through 4F, whereby the flow inlet 51 is switched and successively communicated with the flow outlets 53, 54, 55, and 56 in that order, while, at the same time but with a lag of one step, the flow inlet 52 is switched and successively communicated with the flow outlets 53, 54, 55, and 56. When the valve device in the state indicated in FIG. 4F is further changed over, the device assumes the original state indicated in FIG. 4A, and the inlets 51 and 52 are both cut off from the outlets 53, 54, 55, and 56.

A specific embodiment of structure of the valve device 50 for accomplishing the above described changeover operation will now be described, reference being made to FIGS. through 8, in which parts which have the same functions as those of FIGS] and 4A through 4F are designated by the same reference numerals and letters. The valve device 50 has a valve casing structure 61 of substantially the shape of a hollow cylinder with open ends closed by cover members 62 and 63 secured thereto. A tubular member 64 is fixed at one end to the cover member 62 and extends coaxially into the interior of the valve casing structure 61. This tubular member 62 has a number of holes 65 in its cylindrical wall and has a closed inner end. A pipe line 66 for supplying a first fluid communicatively connected to the other outer end of this tubular member 64.

A valve member 67, inv which the tubular member 64 is fitted, is fitted in turn in the valve casing structure 61 in a manner permitting it to slide and rotate freely relative to the casing structure 61 and the tubular member 64. This valve member 67 at its middle portion facing the tubular member 64 has an internal annular recess 68 and, furthermore, at its right end (as viewed in FIG. 5) facing the valve casing 61 has an external annular recess 69. The recess 68 communicates with a flow inlet 51 by way of the holes 65 in the tubular member 64 unrelatedly to the sliding position described hereinafter of the valve member 67, while the recess 69 is communicating with a flow inlet 52 provided in the valve casing 61. To the inlet 52, there is connected a pipe line 70 for supplying a second fluid.

Around the outer peripheral part of the valve casing structure 61, there are provided four flow outlets 53, 54, 55, and 56 with respective centerlines spaced apart by 60 degrees of angle as shown in FIG. 6. The outlets 53 and 55 are disposed on the same circumference of the casing structure 61, while the outlets 54 and 56 are disposed on the same circumference of the casing 61 at a position offset in the axial direction of the casing by a sliding distance described hereinafter of the valve member 67 from the positions of the outlets 53 and 55. Pipe lines 71, 72, 73, and 74 are respectively connected to these outlets 53, 54, 55, and 56.

The valve member 67 further has a port 75 for communicating with the recess 68. When the valve member 67 is in the position indicated in FIG. 5, the port 75 is coincident with the outlet 55 as indicated in FIGS. 6 and 7, and the pipe line 66 and the inlet 51 are communicating with the outlet 55 and the pipe line 73. In the valve member 67, furthermore, there is formed a communication passage 76 extending in the longitudinal direction of the valve member 67 for the purpose of communicatingwith the recess 69 but avoiding the recess 68 as shown in FIGS. 6 and 8. In addition, holes 77 and 78 are formed to provide communication between the outer periphery of the valve member 67 and the communication passage 76.

These holes 77 and 78 are provided on the centerline of the valve member 67 and are spaced apart by a specific distance in the longitudinal direction of the valve casing structure 61. As indicated in FIG. 8, one of the holes, 77, is tightly closed by the inner peripheral surface of the valve casing 61, but the other hole 78, coincides with the outlet 54, and the pipe lines 70 and 72 are communicative. That is, in the state ofthe valve de- 8 vice shown in FIG. 8,'the inlet 51 is communicative with the outlet 55, while the inlet 52 is communicative with the outlet 54, the changeover valve device being in the state indicated in FIG. 4D.

To the right end part of the valve member 67, there is fixed a piston 79 corresponding to the piston 10 shown in FIG. 1. The piston 79 is slidably and rotatably fitted in the valve casing structure 61 corresponding to the cylinder 11 in FIG. 1 and has around its outer cylindrical surface a zigzag groove 80 similar to that indicated in FIG. 2, and a cam follower 81 embeddedly secured to and projecting inward from the inner wall surface of the valve casing 61 is engaged with this groove 80. To the right end (as viewed in FIG. 8) of the piston 79, there is fixed a disc 83, to the center of which, there is fixed one end of a rod 82 coaxially alined with the valve casing 61 and passing rotatably and slidably through a center hole in the cover member 63. A cap cover 84 is secured to the cover member 63 and houses a hollow shaft '86 supporting integrally a ring-shaped member 85, the hollow shaft 86 being rotatably supported and coaxially alined with the rod 82. A key 87 secured to the other end of the rod 82 is engaged with a key slot 88 formed in the hollow shaft 86 in the longitudinal direction thereof, whereby the rod 82 can slide axially relative to the hollow shaft 86 but rotates unitarily therewith.

With the various parts of this valve in the state described above and indicated in the figures, compressed air is supplied from an air compressor 89 by way of a four way electromagnetic valve 90 into a pipe line 91 and then through a passageway 92 in the cover member 63 into a chamber I to the right (as viewed in FIG. 5) of the piston 79 in the casing 61. The valve member 67, the piston 79, and other parts are then in a state wherein they have rotated to a certain angular position and have moved to their most left ward positions relative to the valve casing 61 and the tubular member 64.

With the various parts in the above described states, in the above described states, the valve device 50 is in the state indicated in FIG. 4D, that is, in FIG. 9A, wherein the port 75 communicating with the inlet 51 is coincidently alined with the outlet 55, and the port 78 communicating with the other inlet 52 is coinciding with the outlet 54. Consequently, a first fluid being supplied through the pipe line 66 is being discharged through the pipe line 73, while a second fluid being supplied through the pipe line is being discharged through the pipe line 72.

.When the above mentioned four-way electromagnetic valve is changed over, the compressed air from the air compressor 89 this time is conducted through a pipe line 93 and, passing through a passageway 94 in the cover member 62, is supplied into a chamber J to the left of the valve member 67 in the valve casing 61, while the pipe line 91 is opened to the outside atmosphere. Consequently, as compressed air is thus supplied into the chamber J, the valve member 67, the pis ton 79, and like parts are moved toward the right. Dur ing this movement, the piston 79 rotates in the clockwise direction as viewed in FIG. 6, its cam groove 80 7 being guided by the cam follower 81, and thus rotates through 60 of angle, as described hereinbefore, while the valve member 67 and the piston 79 move to their most right positions.

During this operation, the port communicating with the inlet 51 and the ports 77 and 78 communicating with the inlet 52 move along the intermittent line in FIG. 9A (in which, for the sake of convenience, the intermittent line is drawn to trace a movement once in the longitudinal direction and then in rotation through 60 of angle). As a consequence, the ports 75, 77 and 78 reach the positions indicated in FIG. 9B, where the port 75 coincides with the outlet 56, and the port 77 coincides with the outlet 55. Accordingly, the first fluid from the pipe line 66 is discharged through the pipe line 74, while the second fluid from the pipe line 70 is discharged through the pipe line 73, through which the first fluid was being discharged until now. That is, the valve device assumes the state indicated in FIG. 4E.

Thereafter, when the four-way electromagnetic valve 90 is further changed over to supply compressed air through the pipe line 91 to the chamber I and simultaneously to oen the pipe line 93 to the atmosphere, the valve member 67, the piston 79, and the like are forced to move leftward and, at the same time, are rotated through 60 of angle in the same direction, the cam groove 80 being guided by the cam follower 81. During this movement, the ports 75, 77, and 78 move as indicated by intermittent line in FIG. 9B, and only the port 78 coincides with the outlet 56. Consequently, from the valve device 50, only the second fluid is discharged through the pipe line 74, through which the first fluid was being discharged until now, and the first fluid is shut off by the valve device. That is, the valve device assumes the state indicated in FIG. 4F.

Thereafter, by changing over the four-way electromagnetic valve 90, the valve member 67 is moved alternately toward the right and left and, moreover, rotated clockwise by increments ofa constant angle thereby to change over the positions of the ports 75, 77, and 78 relative to the outlets 53, 54, 55, and 56, the valve device thereby being changed over successively into the states indicated in FIGS. 4A, 4B, 4C,

A projection 95 provided on the hollow shaft 86 rotating intermittently together with the rod 82 as the valve device is changed over activates limit switches 96 mounted at equally spaced (60) positions on the cover member 63, whereby the changeover positions thereof are verified. In addition, through an open window 97 provided in the cover cap 84, the rotational position of the ring-shaped member 85, that is, the rotational position of the valve member 67, can be verified by visual observation.

By intercoupling the limit switches 96 and the fourway electromagnetic valve 90 and setting the, four-way valve 90 so that it is automatically changed over after a specific constant time from the instant of activation of each switch 96, the above described valve device can be automatically changed over successively and continuously to the six states indicated in FIGS. 4A through 4F.

Furthermore, by changing the construction of the valve member 67, and valve casing 61 housing this valve member, it is possible to provide a valve mechanism accomplishing the same operation described above merely by rotating the valve member 67 by increments of a constant angle or merely by causing it to slide by increments of a constant distance.

As described above, by using the unidirectional rotation actuator of the invention, it is possible to realize changeover valve devices capable of cyclically effecting various valve changing over modes of operation in prescribed sequences.

A changeover valve mechanism of the above described character can be advantageously applied to wide variety of uses, one embodiment of which is a liquid chemical sprinkling system for sprinkling a largescale agricultural farm as described below with reference to FIG. 10. In FIG. 10, parts which are the same or similar to those in FIGS. 5 and 6 are designated by like reference numerals.

In this system, water stored in a water tank 100 is supplied by way of a pipe line 101 to a mixing device 102. Separately, a liquid chemical stored in a liquid chemical tank 103 is pumped by a pump 104 to the mixing device 102, where the liquid chemical and the water are mixed with a prescribed constant ratio. The resulting liquid mixture is sent through a main line 106 and then conducted from the main line 106 to a plurality of branched pipe lines 66a through 6611, being supplied to first flow inlets 51a through 51d of changeover valve devices 50a through 50d shown in FIG. 5.

On one hand, compressed air from an air compressor 107 is supplied through a main line 108 and further through a plurality of branch lines to the second flow inlets 52a through 52d of the valve devices 500 through 50d. At this time, these valve devices 50a through 50d are in the state indicated in FIG. 4B, and diluted chemical liquid conducted through pipe lines 66a through 66d to first flow inlets 51 (as shown in FIG. 5) is conducted by way of outlets 53 to pipe lines 71a through 71d to be sprinklers 109 connected to the outer ends of these pipe lines 71a. through 71d.

After a specific sprinkling time, the valve devices 50a through 50d are switched to the state indicated in FIG.

'4C, whereupon pipe lines 66a through 66d are communicated with pipe lines 7211 through 72d, while pipe lines a through 70a are communicated with pipe lines 710 through 71d. Consequently, the diluted chemical liquid is sprinkled by sprinklers (not shown) connected to the pipe line 72a through 72a. On one hand, compressed air is introduced into the interior of the pipelines 710 through 710', and the chemical solution remaining within these pipe lines 71a through 71:! is

discharged and sprinkled toward the outside by way of sprinklers 109. Thus, undesirable occurrences such as the dripping of residual chemical solution within the pipe lines 71a through 71d onto the areas around the sprinklers 109 and the resulting supply of the chemical solution in large quantity to cause crop damage are prevented.

Furthermore, after sprinkling for a specific time through sprinklers connected to the pipe lines 72a through 72d, the valve devices 50a through 50d are changed over to the state indicated in FIG. 4D. As a result of this valve switching, the pipe lines 66a through 66d are communicated with pipe line, 73a through 73d, and pipe lines 70a through 70d are communicated with pipe lines 72a through 72a. Accordingly, sprinkling of the chemical solution is started anew through sprinklers connected to the pipe lines 73a through 73d, and residual solution within the pipe lines 72a through 72d is discharged by compressed air.

In this manner, the valve devices 50a through 50d are changed over successively from the state indicated in FIG. 48 to that indicated in FIG. 4F, whereby the chemical solution conducted to the pipe lines 660 through 66d is switched and supplied in the sequence through pipe lines 71a through 71d, 72a through 72d, 73a through 73d, and 74a through 74d and sprinkled by sprinklers connected to these pipe lines. At the same time, compressed air introduced through pipe lines 70a through 70a is supplied to the pipe lines immediately after the supply of the chemical solution is shutoff, and residual solution within the pipe lines 71 through 74 is disposed of by discharging and spreading.

When the valve devices 50a through 500' in the state indicated in FIG. 4F are further switched, the valve devices 500 through 50d assume the state indicated in FIG. 4A, and the pipe lines 66a through 6611' and 70a 7 ments but various variations and modifications may be made without departing from the scope and spirit of the invention.

What we claim is:

l. A unidirectional rotation actuator comprising:

a cylinder of hollow cylindrical shape;

a piston fitted within the cylinder so as to be rotatable about and slidable along the axis of the cylinder relative thereto;

means for driving the piston in reciprocating sliding motion relative to the cylinder in the axial direction thereof;

said piston having an outer cylindrical surface facing the inner cylindrical surface of the cylinder, one of said surfaces having a cam groove therein ofa zigzag shape including in continuous alternate combination, substantially straight groove parts of the same inclination in respectively different directions joined end-to-end at bends in the zigzag shape; and a cam follower member fixed to and projecting from the other of said surfaces into engagement in the cam groove, I

said cam groove having guide groove portions respectively provided at said bends. each of said guide groove portions being so shaped that, in concurrence with sliding in one direction of the piston relative to the cylinder, the cam follower member is permitted to advance further along the centerline of one straight groove part of the cam groove beyond the intersection of said centerline and the centerline of the succeeding adjacent straight groove part and, then, in concurrence with sliding of the piston in the direction opposite to said one direction, is permitted to undergo displacement in said sliding direction thereby to abut relatively against one wall surface of said adjacent straight groove part, and

said piston being intermittently rotated in each sliding motion in one direction and the reverse direction.

2. A unidirectional rotation actuator as set forth in claim 1, further comprising a rotatable shaft mounted centrally in said piston and extending axially thereof such that the rotatable shaft rotates unitarily with said piston and is slidable relative to the piston but not slidable relative to the cylinder.

3. A unidirectional rotation actuator as set forth in claim 1, further comprising a valve structure fixed to the piston and having a specific number of valve ports, fluid outlets with which at least one of said specific valve ports communicates in concurrence with unitary rotation through a specific angle of the valve structure with the piston, and means for supplying a fluid to be distributed to the fluid valve ports. 

1. A unidirectional rotation actuator comprising: a cylinder of hollow cylindrical shape; a piston fitted within the cylinder so as to be rotatable about and slidable along the axis of the cylinder relative thereto; means for driving the piston in reciprocating sliding motion relative to the cylinder in the axial direction thereof; said piston having an outer cylindrical surface facing the inner cylindrical surface of the cylinder, one of said surfaces having a cam groove therein of a zigzag shape including in continuous alternate combination, substantially straight groove parts of the same inclination in respectively different directions joined end-to-end at bends in the zigzag shape; and a cam follower member fixed to and projecting from the other of said surfaces into engagement in the cam groove, said cam groove having guide groove portions respectively provided at said bends, each of said guide groove portions being so shaped that, in concurrence with sliding in one direction of the piston relative to the cylinder, the cam follower member is permitted to advance further along the centerline of one straight groove part of the cam groove beyond the intersection of said centerline and the centerline of the succeeding adjacent straight groove part and, then, in concurrence with sliding of the piston in the direction opposite to said one direction, is permitted to undergo displacement in said sliding direction thereby to abut relatively against one wall surface of said adjacent straight groove part, and said piston being intermittently rotated in each sliding motion in one direction and the reverse direction.
 1. A unidirectional rotation actuator comprising: a cylinder of hollow cylindrical shape; a piston fitted within the cylinder so as to be rotatable about and slidable along the axis of the cylinder relative thereto; means for driving the piston in reciprocating sliding motion relative to the cylinder in the axial direction thereof; said piston having an outer cylindrical surface facing the inner cylindrical surface of the cylinder, one of said surfaces having a cam groove therein of a zigzag shape including in continuous alternate combination, substantially straight groove parts of the same inclination in respectively different directions joined end-to-end at bends in the zigzag shape; and a cam follower member fixed to and projecting from the other of said surfaces into engagement in the cam groove, said cam groove having guide groove portions respectively provided at said bends, each of said guide groove portions being so shaped that, in concurrence with sliding in one direction of the piston relative to the cylinder, the cam follower member is permitted to advance further along the centerline of one straight groove part of the cam groove beyond the intersection of said centerline and the centerline of the succeeding adjacent straight groove part and, then, in concurrence with sliding of the piston in the direction opposite to said one direction, is permitted to undergo displacement in said sliding direction thereby to abut relatively against one wall surface of said adjacent straight groove part, and said piston being intermittently rotated in each sliding motion in one direction and the reverse direction.
 2. A unidirectional rotation actuator as set forth in claim 1, further comprising a rotatable shaft mounted centrally in said piston and extending axially thereof such that the rotatable shaft rotates unitarily with said piston and is slidable relative to the piston but not slidable relative to the cylinder. 